H-ZF39 by CDGM

$$n(\lambda) = \sqrt{1 + \frac{0.153634\,\lambda^2}{\lambda^2 - 0.0603806} + \frac{1.54071\,\lambda^2}{\lambda^2 - 0.0118591} + \frac{1.20957\,\lambda^2}{\lambda^2 - 119.98}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[-4.14 \times 10^{-6} + 2(1.44 \times 10^{-8})\,\Delta T + 3(-6.69 \times 10^{-11})\,\Delta T^2 + \frac{8.18 \times 10^{-7} + 2(9.54 \times 10^{-10})\,\Delta T}{\lambda - 0.274}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$